GB698861A - Improvements in or relating to the manufacture of calcium - Google Patents

Abstract

698,861. Distilling calcium and alkali metals. MINISTER OF SUPPLY. Aug. 23, 1946 [Aug. 24, 1945], No. 21826/45. Class 82(i) A process for the purification of calcium, which contains alkali metal as an impurity, comprises distilling the impure calcium in the presence of an inert gas at an absolute pressure not greater than 2mm. of mercury, condensing substantially pure calcium on a condensing surface of iron or a ferrous alloy and condensing the alkali metal on a separate condensing surface, the two condensing surfaces being maintained at suitable temperatures by separate cooling means. The calcium condensate is then separated mechanically from an iron-containing layer. The apparatus shown comprises stainless steel vessel 1 supported in a fused salt bath 3. The still is connected through pipe 12 and valve 13 with a vacuum pump and a source of inert gas. The calcium condenser is formed by a plate 7 cooled by air introduced through pipe 11 and passing over the radial cooling fins 8. As the calcium deposit increases in thickness the flow of air is increased to maintain the correct temperature on the condensation surface. The impurity vapour, e.g. sodium, passes by the annular space around plate 7 and is condensed on the ring 9 which is cooled by flow of water in coil 10. Additional water cooling coils 14 are provided at the joint between vessel 1 and cover 6 and thermocouple sockets 15 and 16 indicate the temperatures at the calcium-condensing surface and in the still respectively. Specification 270,060, [Class 82(i)], is referred to.